In short: GST TDS on works contract comes from section 51 of the CGST Act, 2017. A government department, local authority or Governmental agency deducts one per cent under the central Act, with a matching one per cent under your State Act, where the total value of supply under a contract exceeds Rs 2,50,000. It is calculated on the taxable value, excluding GST. The money is not gone: under section 51(5) it lands in your electronic cash ledger and pays your own GST liability.

The call usually comes at the end of the month. The department has passed your running bill, the amount credited is short of the amount billed, and nobody in the office can tell you which head it went under.

Two per cent on a fifty lakh contract is a lakh rupees. That is worth understanding properly rather than writing off as “government deduction”.

Who deducts, and who does not

Section 51(1) does not apply to everyone who hires you. It lets the Government mandate deduction by a defined list:

  • A department or establishment of the Central Government or a State Government
  • A local authority
  • Governmental agencies
  • Such persons or category of persons as the Government notifies on the recommendations of the Council

That fourth limb is how the net widens over time, and it is the one to check if your client is a public sector undertaking or a special purpose vehicle rather than a department proper.

What matters commercially is the flip side. A private builder, a developer or a main contractor is not in this list unless the Government has notified them into it. If a private client is deducting two per cent from your bill and calling it GST TDS, ask which notification they are acting under. Quite often what they are actually deducting is retention, which is a contract matter and not a tax at all. Our note on retention money in a construction contract deals with that side of it.

GST TDS on works contract starts above Rs 2.5 lakh per contract

The trigger in section 51(1) is a deduction “where the total value of such supply, under a contract, exceeds two lakh and fifty thousand rupees“.

Read those four words carefully: under a contract. The test attaches to the contract, not to the invoice.

So a single work order worth eighteen lakh rupees is inside the net from the first rupee billed, even if you raise it as six running bills of three lakh each. Splitting the billing does not split the contract. Contractors sometimes assume the opposite and are then surprised when the first RA bill comes back short.

What the one per cent is actually calculated on

This is where most of the arithmetic disputes happen, and the Act settles it in one line.

The Explanation to section 51(1) says that for the purpose of this deduction, the value of supply shall be taken as the amount excluding the central tax, State tax, Union territory tax, integrated tax and cess indicated in the invoice.

In other words, the deduction runs on the taxable value, not on the gross amount of the bill.

Line on the bill Treatment for section 51
Taxable value of the work done This is the base
Central tax shown on the invoice Excluded from the base
State or Union territory tax shown Excluded from the base
Integrated tax shown Excluded from the base
Cess shown on the invoice Excluded from the base

A worked example makes it concrete. On a running bill with a taxable value of Rs 10,00,000, the deduction is one per cent under the CGST Act and one per cent under the State Act, so Rs 20,000 in all, worked out on the ten lakh and not on the tax-inclusive total. The tax charged on the invoice sits outside the calculation entirely.

The proviso that switches it off

Section 51(1) carries a proviso that is easy to miss and occasionally saves an argument.

No deduction shall be made if the location of the supplier and the place of supply is in a State or Union territory different from the State or Union territory of registration of the recipient.

The practical case is a contractor registered in one state, executing work in that same state, for a department registered somewhere else. The Act does not ask for a deduction there. If a deductor is taking one anyway on that fact pattern, it is worth raising in writing before the amount is deposited, because unwinding it afterwards is slower than preventing it.

Where the money actually goes

This is the part that turns a grievance into a routine reconciliation.

Section 51(2) requires the deductor to pay the amount to the Government within ten days after the end of the month in which the deduction was made. Section 51(3) requires a certificate of tax deduction at source to be issued in the prescribed form and manner.

Then section 51(5): the deductee shall claim credit, in his electronic cash ledger, of the amount deducted.

Note that it is the cash ledger, not the credit ledger. It behaves like money you have already paid towards GST rather than like input tax credit, and you can set it against your own liability when you file. So the deduction is a timing and cash-flow event, not a cost, provided two things happen: the deductor actually deposits it, and you actually claim it.

That second condition is where money quietly goes missing. If nobody in your office reconciles the deductions against the ledger, the credit sits there unused while you pay your GST in cash. On a business already waiting on delayed payment for government work, that is a self-inflicted squeeze.

It is not the other TDS on the same bill

A single government running bill can carry two deductions with the same three letters, under two different laws. Treating them as one number is a common bookkeeping error.

GST TDS Income-tax TDS
Law CGST Act, section 51 Income-tax law
Threshold Contract value above Rs 2.5 lakh Set under that law separately
Base Taxable value, tax excluded Determined under that law
Where the credit lands Electronic cash ledger under GST Against income-tax liability
Where you reconcile it GST return and ledger Income-tax filing

If your work includes giving machines on hire rather than executing the work yourself, the income-tax side has its own treatment. We covered it separately in TDS on machinery hire charges.

What to do on your side

Three habits cover most of the risk.

Keep the contract value, not just the bill value, visible on your own file, because the Rs 2.5 lakh test runs on the contract. Collect the deduction certificate under section 51(3) rather than relying on the department’s bill sheet. And check the cash ledger monthly against what was deducted, because the credit is only useful once claimed.

One more, for the smaller contractor: if you are weighing the composition route, remember it changes this picture, since you cannot collect tax or claim credit there at all. Read the GST composition scheme for contractors before assuming the two decisions are unrelated. And if you are not yet registered, the GST registration limit for contractors is the prior question.

The bottom line

The shortfall on your government bill is usually section 51 doing exactly what it says. One per cent centrally, one per cent in the state, on the taxable value, once the contract crosses Rs 2.5 lakh.

The money is recoverable against your own GST, so the real cost is the working capital you carry until you claim it, plus whatever you never claim because nobody reconciled the ledger. Tighten that and the deduction stops being a leak.

Bidding for public work and sizing the machine you need for it? Our equipment finance section sets out what lenders look for, and how to bid for government construction tenders covers the paperwork before the first bill is ever raised.

Tax provisions, thresholds and prescribed forms change, and notifications can widen the list of deductors. Confirm current terms with a qualified tax adviser or the official source before relying on any figure here.